Working on boats is one of my mainstays, there are a number of units that will do the job. What I use is a Miller big 40 deluxe with a Hifreq-box not so handy if I can't get within 100' of the truck but, those days are rare and when they do happen I rent a barge and load the truck on it. I also use a spool gun for larger jobs that also hooks right into the machine but I have to be within 30' to make that work.
Hello phaux, you have described a scenario that currently isn't an easy one to deal with. If you use "any" 115 volt inverter capable of welding on aluminum you likely won't have enough power to handle anything much more than possibly 1/16" to 3/32" material thickness. Stick welding on aluminum is probably a last resort type of approach if you have tried welding with that process much. DC tig on aluminum can certainly be done and is done in many cases, it does, however, have some drawbacks as well. I believe, it is best suited to heavier material thicknesses and on materials that can be prepared very cleanly and generally not a repair type situation but more so fabrication related. DC tig for aluminum also requires Helium as a shielding gas. This amounts to requiring higher flow rates for shielding and also somewhat limits it's use in any sort of outdoor scenario.
The way that I generally view work on aluminum goes something like this: if it is heavier material, ie. 1/8" and up in structural or sizeable applications, I would opt for some sort of wirefeed process with a minimum of around 250 amps of power. If the work is smaller in size or has intricasies involved, I would opt for some sort of TIG process: 1/8" or less material thicknesses or smaller parts, a machine of around 180 amps, 1/8" and up, a machine of 200 amps or greater. If portability is an issue I would try to use an inverter power source with AC capability and hi-frequency equipped, otherwise as makeithot mentioned, a multi-process AC/DC portable engine drive that can be equipped with a hi-frequency box or spoolgun is the way to go. Just my $.02. Best regards, Allan